An important point is that the seven reddening indicators we consider here give consistent reddening values for NGC 5548. Although there can be practical problems in determining the quantities going into each individual indicator, and although in some cases the observations were not simultaneous, the agreement in reddening estimates in Table 2 shows that, contrary to previous concerns, there are no major problems with the fundamental intrinsic ratios for these indicators. In particular, this includes the hydrogen lines. We can see from Table 2 that the mean reddening from the three hydrogen line ratios is the same as the mean from the four non-hydrogenic indicators. We thus conclude that what has long been referred to as “the hydrogen-line problem" (Lyman \(\)  being too weak relative to the Balmer lines, and the Balmer decrement being too steep) is not a real problem; it is just a consequence of greatly underestimating the reddening. The same goes for the so-called “Balmer line crisis" (the Balmer lines being too strong relative to the UV lines). The hydrogen line ratios are close to their Case B values. [1]} argues that the reason for this that real BLR clouds are unlike clouds modelled in photoionization codes. The latter are high-column-density clouds which emit only out of the front of the cloud (towards the source of ionizing radiation) or out of the back. Real BLR clouds have lower column densities and readily emit sideways (see Figure 3 of [1]}). This means that optical depths are relatively small.
